As offshore drilling operations progress into deeper waters, usually greater than 1000 feet, dynamically-positioned drilling vessels are used to drill a deep water well. The vessel is usually positioned above a subsea wellhead located on the ocean floor and a pipe assembly, commonly called a riser, is extended downwardly from the vessel to the subsea wellhead.
The lower end of the riser usually contains hydraulically-actuated well control valves and equipment coupling devices used to connect the lower end of the riser to the subsea wellhead. Pressurized hydraulic fluid supplied from the drilling vessel via hydraulic cables is used to actuate these hydraulic devices.
At times, the hydraulic cables become damaged during drilling operations, thereby severing the source of pressurized hydraulic fluid that is supplied to the hydraulically-actuated devices. At other times subsurface electric power or control circuit or component failure can render normal direct wire control of blow out preventer functions inoperable.
Without assistance of divers or remotely operated vehicles (R.0.V.'s), the entire riser assembly would have to be retrieved to the surface to repair the hydraulic or electric system failure, an operation that would require the retrieval of thousands of feet of riser pipe at a cost of up to a million dollars.
Since divers cannot be safely used to repair subsea equipment which is located at depths which may approach 7,000 feet, the task of repairing the hydraulic or electric system failure would depend on a R.0.V., if the R.0.V. is capable of performing the system repair operation.
Repair of such subsea hydraulic or electric circuits underwater is usually not feasible because of requirements for detailed disassembly and use of diagnostic instruments. The equipment must usually be brought to the surface for repair.
In the event of such failures, it is sometimes necessary to provide emergency operation of some blow out preventer (B.0.P.) functions to close in the well so that the control packages on the Lower Marine Riser Package can be recovered to the surface safely or to disconnect the main B.0.P. stack connector from the wellhead to recover the whole stack.
In the past, emergency hydraulic connections were made to connect an emergency pump on the R.0.V. system to the B.0.P. function using snap sleeve connectors designed for quick connection of hydraulic lines by human hands. These have been found to be easily damaged and difficult to stab when used by a more powerful but clumsy R.0.V.
Applicant is not aware of any prior art which, in his judgment as one skilled in this particular art, would anticipate or render obvious the present invention. However, for the purpose of fully developing the background of the invention and establishing the state of the requisite art, the following art is set forth: U.S. Pat. Nos. 3,846,922;, 3,482,410; 4,533,162; 3,052,299; 3,967,462; 3,899,199; 3,345,085; and 4,601,608.